Broaching machine



Dec. 18, 1934. F. J. LAPOINTE 1,984,974

BROACHING MACHINE Filed Dec. 16, 1952 5 Sheng-sheet 1` Dec. 18, 1934.F.,J. LAPOINTE 1,984,974 I BROACHING MACHINE Filed Deo. 1e, -1952 5sheets-shea 2 Dec. 18, 1934. F. .1. LAPOINTE BROACHING MACHINEFiled'Deo. 16, 1952 5 Sheets-Sheet 3 Dec. 18, 1934. F. .1, LAPOINTEBHOACHING MACHINE .Filed DSC. 16, 1932 5 Sheets-Sheet 4 ne@ 1s, 1934.

F. J. LAPOINTE BROACHING MACHINE Filed Dec. 16; 1952 5 sheets-sheet 5 I,I l I l Patented Dec. 18, 1934 UNITED STATES PATENTA OFFICE i v l1,934,974

BROACHING MACHINE Francis J. Lapointe, Ann Arbor, Mich. ApplicationDecember 16, 1932, Serial No. 647,633

`10 Claims.

My invention has for its object to provide an eiiicient means forautomatically momentarily releasing or cushioning the pressuretransmitted from a driving means to a member actuated thereby with theobject of preventing a pressure upon the actuated device beyond thatnormally sustainable thereby. The invention is particularly applicableto machines wherein the ele-f ments used to form articles are of acharacter that for efficient operation should be actuated'at a pressureor by a force that is belowa certain maximum` when performing thefunction for which the elements are designed, or to prevent theiroperation under a pressure in excess to that which they can normallystand Without risk of injury. The invention thus provides an efficientymeans for the maintenance of the operation' of the elements, such ascutting operations, and prevent breakage where, by reason of theirpeculiar construction, one or more of their sections are of such `acharacter as to'have a relatively '1 small safety factor.

The invention provides a means for limiting* the pressure exerted on themachining element to apoint below a predetermined maximum and thusoperates to automatically protect the lelement from injury. :y

The invention also provides an indicator for indicating continuously thechanges in pressure required to move the machining element and therebyindicate the change in the condition of element While in use and thecondition of the material being operated upon. Thus, by my invention1the condition of a tool, such as a cutting tool, is automaticallyindicated or an unusual hardness of the material is indicated, as isoften found in connection with work on any particular product formed ofa plurality of like articles. Indication will be given as to whether theWork on the particular article shall progress further or whether thetool should be replaced or resharpenedor reformed, or a new tool shouldbe inserted in place of the one that'givesY indicationy containing theinvention may partake of different forms and may be varied in theirdetails and still embody the invention. To illustrate a practicalapplication of the invention, I'have selecteda broaching .machineembodying the inventionas an example ofthe various structures and thedetails of such structures that contain the invention and shall describethe selected structure hereinafter, it being understood that variationsmay be kmade and that certain features of my invention may be used toadvantage without a corresponding use of other features of theinvention,j and without departing from the spirit of the invention.'I'he particular structure selected is shown in the accompanyingdrawings.

Fig. 1 illustrates a vertical section of the broaching machineselectedas an example of the embodiment of: the invention. Fig. 2 illustrates acontrol lever and a side view of fa tool elevator for `manipulating thebroaching tool to enable replacement vof the work. Fig. 3 illustrates afront view of the machine. Fig. 4 illustrates a viewof a',k section ofthe machine showing a rack and pinion that'foperates the guide plate andthe drawhead of the broaching machine. Fig. 5 illustrates a View of asection taken on the plane of the line 5-5 indicated in Fig. 1. Fig. 6illustrates a view of a section taken on the plane of. the line'6-6indicated in Fig. 5. trates' a view of a section taken on the plane ofthe line .7-7 indicated in Fig. V5 and particularly illustrates valvesfor controlling the flow of a iluid to and from the drawhead of thebroaching machine. part of the machine and particularly illustratesswitches that are controlled raccording to the Fig. 7 illus-vFigfillustrates a broken view of a i extent ofmovement of the broachingtool. Fig. 9

illustrates a side'view of a cam block used for manipulating theswitches.

Y In the particular form of construction shown in the drawings, adrawhead 1 is connectedto a'guide plate 2 thatis vertically reciprocablymounted in aframe 3 having suitable ways 4 for guiding the plate 2. vThe plate 2 is reciprocated by means of a rack 5 connected to the plate2 and a pinion 6 driven by a suitable electric motor 7, through'reducing gear, such as the gear Wheel 8, `the worm 9, a worm wheel 10which is connected to the shaft 11 to which is keyed, or on which isformed, the pinion 6. 'I'hese parts are suitably r mounted in the frame3. The worm 9 and worm o movements of the breach head as guided by theplate 2 and the frame 3 of the machine.

A suitable chuck 16 is connected to the drawhead 1. The chuck 16 is ofthe type illustrated and described in the Lapointe application No.517,336, filed February 21, 1931, it being provided with means forengaging the breach when pressure a spring pressed collar i7 isreleased. Disengagement with the breach is produced by the descent ofthe drawhead 1 so as to press the collar 17 .of Athe chuck 1.6 againstthe work plate or some part connected therewith. The breach 18 isprovided with a breach head 1.9- that is connected to the body of thebreach by means of a neck 20 that is engaged by suitable dogs asdescribed in the said Lapointe applicatien and illustrated,particularly, in Fig. 5.

The drawhead 1 is located above 'the' work plate 2l and, te enableinsertion of work below the werk plate, the upper end of the breach isposition-ed well below the work plate. To connect the breach 18 with thedrawhead, the breach is raised and insertedk through the Work and thework plate and into the chuck 16 and held against the drawhead and, whenthe drawheadl is raised so as to relieve the pressure of the werk plateagainst the collarl'?, the breach head is engaged in the chuck.Whereupon the breach is pulled through the work by the operation of thepinion 6 that meshes with the rack 5 that is connected to the guideplate 2.

As is well known in connection with mechanical-l a number of articles oflike character there will,

often be a great variation in the hardness, or elasticity, of portionsof the articles. There will be seme that will be exceedingly hard wherevothers will be relatively soft and also parts of any one article may bemuch softer than other parts, hence kthe breaching tool will belsubject'to varying cutting resistance in connection with any particularbreaching operation. Where uniform movement of the breach is produced,notwithstanding variatien in cutting resistance, breaches will be brokenor teeth of the breach will be chipped or nicked, or where the hardnessdiffersv in; the articles of like character being breached, the teethwill dull at varying rates, increasing the cutting resistance at varyingrates. Also, where large holes are being cut and large teeth arerequired to withstand the cutting strain, requiring considerableclearance for chips and consequently requiring increased distancesbetween the cutting edges of consecutive teeth, there is produced alarge variation in the tool resistance as the number of teeth in contactwith the surface of the article being cut is Varied. Where the teeth arelarge the cutting resistance may vary as much as 20%, as'where fourteethare in contact with the article and a fifth engages, subsequentlyone of the teeth leaves the article, followed by a tooth entering intoor engaging withan article. Also, as is well known in connection withbreaching operations, breaches partake of different forms in their crosssections as for cutting slots or square holes or hexes or oblong holesor chane nels, or undercutting sides of holes or slots, etc. In order toform such slots er openings intel-their characteristic shapes, breachesmust necessarily be so constructed as to provide teeth havingcerresponding shapes and provision must be made f er clearance and forgathering of the chips within the article from each teeth as itprogresses in the article, which results in varying shapes of the shanksor bodies of the breach, particularly the portions located intermediatethe teeth. Frequently the cross sectional area of the body of the breachis very slender and of such cross sections as is necessitated by theconfiguration of the cutting edge and the necessity of provision ofclearance and spaces between the teeth for gathering the chips. Thisfrequently necessitates designing breaches within a narrow margin ofsafety, er with a small safety factor, and while themechanicallyoperated breach machines are desirable because of theirpesitiveness and uniformity of movement and their speed control, yet forthe same reason they fracture breaches because of lack of give erresiliency. Also the practical irresisting forward drive of the breachfrequently causes fracture of the heavier breaches by reason of the factthat the spring lof the metal of the breaches, when subject to highpressure, causes fracture in the whip back and back lash as theconsecutive teeth enter and leave the material. The advantageousfeatures of mechanically driven breaches are retained and thedisadvantages eliminated, in my invention, by providing a regulatablecushioning yielding means between the breach and the breach actuatingelement.

The breach being light in weight, or small'in mass, it is exactlyresponsive in its tensiente the variation in cutting resistance and whenyieldingly connected, as. distinct from elastically connected, te thepressure head of thcmachine, it changes in movement in response toresistance tomovement. While the mechanically operated driving membermoves at a uniform speed, irrcspective tothe tool resistance, theinvention-provides for cushioning the breach in its movement relativetothe driving. member. This eliminates breaking ofthe teeth, er fractureof the body of thezbroach, caused by jarring, or bumping of the teethproduced by subjecting one or more of the teeth, within an exceedinglyshort time, to a pressure that exceeds their elastic limit. |Theinvention provides a means that enables the breach to adjust itself by amomentary diminution of the pressure when it reaches er approximateswhat may be considered an excess, although the drawhead moves steadilyforward regardless of such changes in pressure.

The invention also provides a means for indicating the cuttingresistance to which the breach is subjected whereby increasing dullness,although at varying rates, may be readily noted, Also` exceedingly hardarticles in any particular product may be quickly noted and the machinestopped, or the characteristic hardness of the articles may beinvestigated and the articles may be assorted as to their hardness andanother breach used for cutting the harder articles or a slower speedused. Thus my invention enables operation of breaching machines at amaximum speed .and `results in a great saving in cest of operation. Byreason of the indicated tool resistance, it enables a very greatlyincreased breaching rate since it enables speeding up of breachingmachines to the maximum safe rate.

ln order te obtain these advantageous results in the particular form ofconstruction selected as an example of an embodiment. of my invention,the breach 1,8 is directly connected te a fluid fi i) pressed piston 26by means of the chuck 16 and portions v,of the fluid are allowed toescape when the pulling pressure exceeds a safe maximum, the cylinder 27in which the piston is located forming a reservoir of the fluid in anamount suiiicient to meet exigencies of cutting resistance variationsfor which fthe machine is designed. The escape of the fluid eliminatesthe reactions of elasticity.v

and the whip-like action caused thereby.

The piston rod 25, the piston 26 and the cylinder 27 form a part of thedrawhead 1. The cylinder 27 is charged with oil under pressure by meansof the pump 28 that is operated by the electric motor 29. The pump 28 islocated in the reservoir 30 that operatesto force the oil under pressurethrough the pipes 32 and 33, the passageway 35 formed in the plate 2 andthe drawhead l to the cylinder 27.v The passageway 35 opens into thelower end of the cylinder 27 and beneath the piston 26 and operates topress the piston 26 towards the upper end of the cylinder 27. A suitableengaging screw or stop 36 may be provided in the upper end of thecylinder 27 to adjustably limit the upward movement of the piston 26 andthus limit the o-il content of the cylinder and thus limit the slackbetween the stroke of the broach head and the broach.

When the drawhead 1 is raised by the opera` tion of the pinion 6, theoil located below the piston 26 is subjected to a pressure dependingupon the cutting resistance to which the broach 18 is subjected andconsequently the piston 26 will give according to the flow of the oilfrom the cylinder.` The piston, however, being subject at A all times toa pressure at least equal to that producible by the pump 28 is returnedto the upper end of the cylinder and the cylinder charged with a freshsupply of oil upon completion of the working stroke of the broach. Thepressure during the working stroke rises well above the pressure thatmay be'prcduced vby the pump 28 by reason of the fact that the oil thatpasses through the passageway 35 is trapped bymeans of the oneway springpressedvalve 40. The valve 40 allows substantially free movement of theoil from the pipe 34 into the passageway 35 but operates to preventanyreturn of oil into the pipe 34 and consequently any counter pressureon the pump 28. Thus by a relative small pump the advantages of myinvention may be produced.

The oil may escape from the cylinder only when it reaches apredetermined pressure as determined by an adjustable spring pressedneedle valve 43 located in an opening 44 having a small port and formedin a sleeve 45. The sleeve 45 is located in the drawhead 1. The needlevalve 43 is provided with a head 46 that is spring pressed by means ofthe spring 47. The tension of the spring 47 may be adjusted by means ofthe screw 48 having the knurled head 49. If desired, a nut 50 may beprovided for frictionally securing the screw 48 in its adjustedposition. The bore 44 is exceedingly small, ap-

proximating capillaric size and communicates with the passageway 35 thatleads to the lower end of the cylinder 27 and the end of the needle 43is located in proximity to a passageway 51 extending at right angles tothe opening 44. The passageway 51 communicates with the passageway 44when the end of the needle is removed from the passageway 44 and thusallows a very ne stream of oil to escape from the passageway 35 andconsequently from the cylinder 27. The opening 44 being practicallycapillaric in size, the amount of escape of oil is very minute upon eachapplication of excess pressure, that is, pressure in excess of thatdetermined by the pressure of the spring 47. The pressure immediatelylowers by reason of the release of this minute quantity o oil whichgives opportunity for the broaching tool to adjust itself to the cuttingresistance produced by any onev of the various circumstances orconditions as to change in number of teeth engaging the article ormomentary change in' cutting resistance due to local characteristicchange in a minute part of they material or due to a fracture of thetooth near the cutting edge or due to momentaryfailure of delivery ofchips from the cutting edges. In other words, it affords a yieldingvmeans directly connected to the broachto enable the broach to readilychange its speed and yieldingly over-` come the resistance to itsmovement without being subject to any resiliency of the fluid or air inthe oil and allow the tool to gradually adjust itself to its ownelasticity.

In order to readilycontrol the transmissible pressure between thepressure head and the broach, a pressure indicator 54, of any suitabletype, may be connected to the lower end of the cylinder, such as throughthe passageway 55. The indicator 54 is mounted on the drawhead 1 andindicates the pressure of thev oil in the cyl-V inder 27 andconsequently the resistance to movement met by the broaching tool.breaching operation on the product or in vusing a new broach, thecutting resistance will be noted^and the pressure within the cylinderr27 may be promptly varied accordingly by the adjustmentxof the tensionof the spring 47. When f a large broach is used the tension oi thespring is raised and the variations in the cutting resistance, as theteeth pass over the work, is noted and adjustments made to afford thedesired lgive in the pressure, according to the changes in resistance tomovement of the tool, and thus produce the desired protective yield. Asthe broaching operation progresses,` increased dullness of one or moreof its teeth is indicated. by a gradual increased pressure. Quite suddenthough uniform rate of change will vindicate increased dullnessanddecrease in chip delivery from the edges or burnishing of the work atthe edges of one or more of its teeth. There will be variations ofmovement of the indicator by reason of the teeth entering and leavingthe work which is noted and allowed for and bumping prevented. Markedrise in the indicator will indicate either local hardness of portions ofthe article being broached or fracture yof broach edges which may beimmediately determined by,k

examination of the broach and which will require variation either toraise the pressure transmissible to the broach o1' to allow for decreaseof pressure by allowing the escape of oil in slightly increased, thoughstill minute, quantities to increase the give or cushioning effect ofthe oil.

When these conditions are revealed through the indicator, suitablealterations may be made.

The oil that is allowed to escape from the-cylinder is returned tothe'reservoir 30 through the passageway 52 and pipes 53, 56 and 57. Thecylinder 27 andthe drawhead'l are provided with a passageway for thedischarge of any oil that may accumulate in the upper end of thecylinder to the passageway 52 which is con--` nected to the reservoir.This prevents blocking of the piston when the cylinder is filled. Thedrawhead is also provided with apassageway l61 In starting the l Cirwhich will draw off the oil that passes the pack`- ing of the piston rod25.k

The pipes 34 and 53 telescope within the pipes 33 and 56 respectively.Suitable packing glands being provided in the xture 64 located at theupper ends of the pipes 33 and 56 prevent the escape of oil from thepipes at the telescopic connections. The pipes 34 and 53 are connectedte the guide plate 2 and move vertically within the pipes 33 and 56respectively to maintain the tric current and for making thedisconnection with the source and for reversing the motor. The switchesand circuit controlling devices will vary according to the character ofthe motor as to whether a direct current motor or an alter' natingcurrent is used and, if alternating, the switching devices and electricsystem will vary according to the phases of the current. These featuresform no part of my invention and provide merely the means for connectingand disconnecting the motor or for reversing the motor. In order thatthe motor may be disconnected er may be reversed, I have providedswitches contained in switch boxes 66 and 67 having arms 68 and 69 thatcarry rollers 70 and 71. The arms 68 and 69 are connected to suitableswitch arms that operate the movable contacts of the switches and whenoperated they either open or reverse the meter current. The switchcontained in the bex 66 is operatedto open the circuit of the meter byan adjustable cam 73 connected to ablock 74, While the switch containedin the box 67 operates to reverse the motor by means of the cam 75connected to the block 76. The cam 75 operates to raise the roller 71and swing the arm 69 te reverse the current when the drawhead is raisedsuiiiciently to complete the movement of f the teeth of the breach 18through the work but leaving in the work the pilot 77 to guide it en thereturn stroke of the drawhead.

The blocks 74 and 76 are adjustably secured in the frame 3 of themachine and particularly in a slet 78 by' means of suitable bolts 79that extend through the slot and clamp the blocks in desired positionsto cause reversal of the motor at the desired point in the operation ofthe breach and to open the circuit of the meterA upon completion of thereturn of the drawhead 1. The switch boxes 66 and 67 are supported onthe guide plate 2 and in position te be operated by the cams 73 and 75located on the frame 3.

When the drawhead returns and presses the collar 17 against the workplate 31, the chuck 16 releases the breach head and delivers the breachte a means for lewerincr the breach to a peint well below the work plateto enable insertion of the work intermediate the head oi the breach andthe work plate. When the Work has been placed in position, the breach isthen raised to insert its head into the chuck and the motor 7 is startedby the operation of a suitable switch which raises the drawhead l,allows the chuck to engage the kbreach head and draw the breach throughthe A iixed piston 82 having a hollow stem 83 is cennec-ted by means ofa pipe 84 te the pipe 32, the valve 85 and the pipe 86. When the valve85 is operated the cylinder 88 is emptied through the hollow piston' red83, the pipe 84, the valve 85 and the pipe 87 which is connected tothepipe 5'7 that leads to the reservoir. The valve 85 may be operated bya suitable pedal lever 89. When, therefore, the breach 18 is to beraised, the lever 89 is depressed and the valve is shifted to connectthe pipe 84 withl the pump 28 through the pipe 32. This directs the eilunder pressure to the upper end of the cylinder through the hollowpiston rod 83 and raises the breach 18 te locate the breach head 19within the chuck of the draw'- head. A switch is operated for closingthe circuit of the motor and the d'rawplate and drawhead are raised bythe operation of the pinion 6, the pressure in the cylinder 88 causingthe breach to follow up the drawhea'd until the breach is locked in thechuck. The drawhead continues to move up until the werking is completed.The motor is then reversed and the drawhead then descends, the cylinder88 being held up bythe pressure of the oil that is inserted in the upperend of the cylinder, While the lever 89 is held down by the operator.When the drawhead reachces the lower peint in its travel the chuck isopened and the breach is released and the motor circuit is opened, theoperator then releases the lever 89 and allows the escape of oil te thereservoir through the valve 85k and the cylinder 38 together with thebreach 18 descends by the weight of the cylinder. If desired, the lever89 may be released upon locking the breach in the chuck. This permitsthe immediate return of the cylinder 88, the chuck operating to drop thebreach, the lower end entering the socket 91, upon the completion of thereturn movement of the drawhead. l

I claim: a

l. ln a machine, a drawhead, means for reciprocating the drawhead, areciprocable machine member, a cylinder and piston for connecting thereciprecable member to the drawhead, means for introducing `a iiuid intethe cylinder and an indicating means for indicating the resistance tomovement of the reciprocable machine member, means for maintaining asupply of fluid in the cylinder and means for varying the pressure ofthe iiuid in the cylinder.

2. In a breaching machine, va drawhead, a means for reciprocating thedrawhead, a breaching tool, a vcylinder and piston for connecting thebreaching tool to the drawhead, a source ofy supply of iiuid underpressure, means for connecting the said source of supply with the saidcylinder, means for indicating the pressure transmitted through thefluid by the movement of the drawheaol when actuating the breaching tooland means for releasing the pressure of the fluid in the cylinder.

3. In a breaching machine, a guide plate, a rack connected to the guideplate, a drawhead connected to the guide plate, a breaching tool, acylinder and piston for connecting the breachtool to the drawhead, asource of supply of iiuid under pressure, means for connecting the saidsource of supply with the cylinder, adjustable means for varying theresistance te the return new of fluid in the cylinder to the source oimeans ier indicating the pressure of the fluid in the cylinder.

4. ln a breaching machine, a guide plate, a rack connected to the guideplate, a pinionv for raising and .lowering the rack, a frame, a werkplate connected to the frame, a drawhead connected te the guide plateand located above .the vwerk-plate, a breach tool, anautomatic chuck forengaging the breaching tool fer releasing the breaching tool when`pressed against the werk plate, a cylinder and piston` for connectingthe chuck `te the drawhead, a source of supply ef fluid under pressuremeans for connecting the said source of supply with the cylinder, andmeans for varying the pressure transmissible through the fluid in thecylinder te the chuck.

5. In a breaching machine, a guide plate, a rack connected te the guideplate, a pinion for raising and lowering the rack, a frame, a werk plateconnected te the frame, a drawhead connected te the guide plate andlocated above the work plate, a breaching tool, an automatic chuck forengaging the breaching tool for releasing the breaching tool whenpressed against the werk plate, a cylinder and piston for connecting thechuck to the drawhead, a source of supply of fluid under pressure, meansfor connecting the said source of supply with the cylinder, means forvarying the pressure transmissible through the iluid in the cylinder tothe chuck, and a cylinder and piston for lowering and raising thebreaching tool from the chuck when the chuck engages the werk plate, andmeans for connecting the last named cylinder with the source of supplyunder pressure.

Y 6. In a breaching machine, a draw head means for reciprocating thedraw head, the cylinder mounted on the draw head, a piston located inthe cylinder, a breaching tool connected te the piston, a source ofsupply of iiuid under pressure connected to the cylinder at a peintlocated en the side of the piston on which the breaching tool is locatedfor transmitting pressure from the draw head te the breaching toolduring the working stroke, a pressure indicating means cennected to thecylinder en the breach side of the piston, the machine having apassageway cennected te the source ef supply and te the cylinder en thebreach side of the piston, and an adjustable valve, located in thepassageway for varying the pressure transmitted from the draw head tethe breaching teel.

7. In a breaching machine a pressure head, means for reciprocating thepressure head, a cylinder, mounted on the pressure head, a pistonlocated in the cylinder, a breaching tool connected te the piston,arseurce of supply of fluid, a pressure means for subjecting the fluidto pressure, the machine having a passageway for cenducting the fluidunder pressure te the cylinder at a peint located on one side of thepiston, a one way Valve located in the passageway for preventing returnilew of the fluid tothe pressure means, the machine having a returnpassageway connected rte the cylinder en the said one side of the pistonand to the source of iluid supply, and a pressure control valve locatedin the said return passageway and opened by the pressure of the fluid inthe said return passageway, a spring for counteracting the fluidpressure on the pressure control valve and normally operating tomaintain the control valve closed against the pressure of uid in thecylinder, and means for adjusting the pressure of the spring te adjustthe maximum pressure transmissible from the cylinder te the piston telimit the actuating pressure exerted by the pressure head en the toolduring their working strokes.

f. 8.`In,a breaching machine .a pressure head, means forfreciprecatingAthe pressure head, a cylindery mounted onthe pressure head, a piston.located in the'cylinder, a breaching tool cennected tothe piston, asource of supply of fluid,

a pressure means for subjecting the fluid te pressure, the machinehaving a passageway for cenducting the lluid under pressure to thecylinder at a peint located en one side of the piston, a one way valvelocated in the passageway for preventing return flew of the fluid te thepressure means, the machine having a return pas'- sageway connected tethe cylinder en the said ene side of the piston and to the source offluid supply, and a pressure control Valve located in the said returnpassageway and opened by they pressure of the fluid in the said returnpassageway, a spring for counteracting the fluid pressure on thepressure control Valve and normally operating te maintain the controlvalve closed against the pressure ef uid in the cylinder, means foradjusting the spring, for varying the limit of pressure transmissiblefrom the cylinder to the piston, andan adjustable step located withinthe cylinder for limiting the movement of the piston relative to' thecylinder in a direction away from the said one side of the piston forlimiting the slack between the pressure head stroke and the breachmovement `produced by fluid escapement te the said source of supply ofiluid.

9. I n a breaching machine, a draw head, means for reciprocating thedraw head, a cylinder mounted en the draw head, a piston located in thecylinder, a breaching teel connected to the piston, a source of supplyof iluid, a pressure means for subjecting the fluid to pressure, apassageway for conducting the fluid under pressure to the cylinder at apeint located on the side of the piston en which the breaching tool islocated, a one way valve located in the passageway for preventing returnilow of the iluid. to the pressure means, the machine having a returnpassageway connected to the cylinder on the breaching side of the pistonand to the source of iiuid supply, and a pressure control valve'lecatedin the said return passageway, a spring for counteracting the iluidpressure en the cent1-ol valve and normally operating to maintain 'the jcontrol valve closed against the pressure of fluid in the cylinder, andmeans fer adjusting the pressure ef the spring for adjusting thepressure transmissible from the draw head te the breach- .ing tool andlimiting the draft pressure on the tool and easing the movement of theteel relative to the draw head.

10. InV a breaching machine, a draw head, means for reciprocating thedraw head, a cylinder mounted on the draw head, a piston located in thecylinder, a breaching tool connected te the piston, a source of supplyof fluid, a pressure means for subjecting the iluid to pressure, apassageway for conducting the iluid under pressure to the cylinder at apoint located en the side of the piston en which the breaching tool islocated, a one way valve located in the passageway forpreventing returnflow of the fluid to the pressure means, the machine having a returnpassageway connected to the cylinder on the breaching side of the pistonand to the source of iiuid supply and a pressure control valve locatedin the said return passageway, a spring for ceunteracting the fluidpressure on the control valve and normally operating to maintain thecontrol Valve closed against the pressure of fluid in the cylinder,means for adjusting the pressure ,in which the broaching tool is drawnby the of the spring for adjusting the maximum presdraw head forvlimiting the slack between the sure transmissible from the drawhead tothe draw head stroke and the broach movement pro.- broaehing tool, andan adjustablestop located duced by fluid escapement through the said re-5 within the cylinder for limiting the movement turn passageway.

of the piston relative tothe cylinder in a direction FRANCIS J.LAPOINTE.

